A few months ago, we showed you this strange structure found and photographed by graduate student Troy Alexander in the Peruvian Amazon. As far as we knew, no one had ever seen anything like it before. Was it built by an insect, a spider, a fungus, or space aliens? Researchers at the Tambopata Research Center kept observing this and other structures like it until they figured it out.

Photographer Jeff Cremer and entomologist Phil Torres tell us how the creature that made the structures was found.

A two week effort led by Phil Torres at the Tambopata Research Center, a jungle lodge in Peru, finally put to rest what had baffled both researchers and thousands of online commenters: the structure was created by a spider.

Images of this structure first went viral in August of 2013 when researcher Troy Alexander encountered two of them on an island in Tambopata, Peru, took photos to document them, and posted the pictures to reddit.

The images were shared widely on that site and throughout the internet, with no clear answers as to what made it, theories ranged from a fungus to a spider, and even space aliens.

Teaming up with Lary Reeves and Geena Hill from the University of Florida, Torres set out to the same island to see if they could find more, and ideally to see if they could catch it being made in action.

A mite near the web structure. (Image credit: Jeff Cremer/Perunature.com)

“The most challenging part of the search was that we had so little to go on- should we be eyeing every spider we see suspiciously, or was something flying around and creating these?” said Torres.

After careful macro photography by wildlife photographer Jeff Cremer, the team isolated some of the structures to see what, if anything, hatched out of them.

After several days of nothing hatching and inconclusive dissections, the team was ready to call the structures an elaborate spermatophore created by a spider, basically a package of sperm typically paired with nutrients designed to entice, fertilize, and feed a female.

On the final morning of their excursion, two of the structures hatched out one spiderling each, and the next day a third did the same.

This makes the structure potentially the first documented case of a spider laying a single egg in an egg sac, as they traditionally lay multiple.